The present invention relates generally to fluid conveying pipe systems and, more particularly, to mechanical couplings used in such pipe systems, for example, to join pipes with other pipes or with pipe fittings.
Various forms of pipe systems are well known for use in diverse applications, ranging for example from plumbing systems conveying potable drinking water under pressure, to waste water systems, often referred to as drain/waste/vent (or DWV) systems, conveying sewage and gray water gravitationally under neutral pressure, to laboratory and other systems conveying potentially dangerous chemical liquids and gases.
Essentially all such pipe systems are fabricated of a network of straight pipe sections coupled together with various fittings. Depending on the application, pipe sections and fittings may be formed of various materials, typically either metallic materials such as cast-iron, galvanized steel and copper, or plastic materials, such as PVC (polyvinyl chloride), PP (polypropylene), ABS (acrylonitrile butadiene styrene), or PE (polyethylene). In substantially all cases, the coupling joints in a pipe system must be secure against leakage. In most plastic pipe systems, this is accomplished by the use of a cement or other chemical bonding agent suitable to establish a chemical bond between pipe sections and fittings.
While bonded couplings provide reliable and secure joints between pipe sections and fittings in plastic pipe systems, the use of cements and bonding agents is increasingly disfavored and coming under increasing regulatory scrutiny because of potential environmental dangers presented by the chemicals utilized. While considerable effort has been devoted toward the development of alternative mechanical forms of pipe joints or couplings in plastic pipe systems, such mechanical couplings have yet to become widely accepted and in many cases still fail to meet local codes. For example, most local plumbing codes governing DWV systems still require the use of chemical bonding agents. There is accordingly a need within the plastic pipe industry for a satisfactory form of coupling assembly by which pipes and fittings may be mechanically joined without requiring the use of any adhesive or bonding agent.